Coated iron or steel article and method of making the same



Patented May 23, 1933 UNITED- STATES PATENT ori ice EDWARD J. P. FISHER AND CLYDE G. CRANE, 0F PEORIA, ILLINOTS, ASSIGNORS I0 KEYSTONE STEEL & WIRE ILLINOIS COMPANY, or rnonm, rumors, A oonrom'rron or ooa'rnn most on s'rnnr. ARTICLE AND amn on or Maxine rm; am

No Drawing.

This invention has reference to a zinccoated iron or steel article and to the.process of producing such an article, which con sists in subjecting the article base to a phosphorizing medium at a temperature and for a period of time suflicient to produce a thin surface layer of high phosphorus content as an integral part of said base, and subsequently zinc-coating said base bythe hotdip galvanizing process.

The invention comprehends primarily the.

producing of galvanized wire, particularly for telephone and other electrical transmission lines; although the invention may be found useful in the coating of other iron or steel articles as, for example, sheets, strips and the like.

In the application of the invention to the ties than those found in telephone w1re man ufactured from high phosphorus steel.

, In the practice of the invention, when applied to the zinc-coating of wire, the base wire of any suitable gauge is treated at an elevated temperature in an atmosphere of phosphine (PI-I gas whereby the phosphorus content of the surface layer of the base wire is increased. This phosphorizing action occurs when the phosphine gas comes in contact with the surface of the hot base wire whereby it is dissociated into its elements phosphorus and hydrogen, the phosphorus atoms being physically absorbed in the surface layer of the base wire. -While we have described the dissociation of the phosphine-gas at the surface of the hot wire, this is not essential to the practice of the "invention as the hot wire could easily be phosphorized by the physical absorption of place.

Application filed August 5, 1932. Serial No. 627,602.

phosphorus atoms into its surface layer .from a gaseous mixture of phosphorus and some non-oxidizing gas such as hydrogen. In any case such phosphorizing action could be'a physical reaction, that is,the physical absorption or solid solution or diffuslon'of phosphorus atoms into the surface layer of the steel base. i

The temperature at which the wire is phosphorized may be sufficient to simultaneously anneal it, and we prefer to take advantage of this effect; however, we realize that the annealing treatment may be accomplished either before or after such phosphorizingtreatment. When the phosphorized base wire is subsequently galvanized a w1re is produced with a heavy and tightly adherent zinc coating which will withstand severe bending and forming without flaking or peeling of the zinc coating.

In the application of the zinc .to such phosphorized base wire the coating may be i obtained by the use of the ordinary method of hot-dip galvanizing when applying the zinc to the phosphorized surface of the ironbase body resulting in obtaining a tightly adheringheavy zinc coating on such a conditioned surface. However, practice may. determine that zinc coatings (fully as adherent) may be applied to the phosphorized surface of the ferrous base by other methods of zinc coating wherein an alloying action between the zinc'and the ferrous base takes 'We are aware that in the production of open or rimmed steel phosphorus is added to the. molten steel to make it possible to obtain an adherent zinc coating by galvan 'izing articles made from such steel. The

presence of the added phosphorus in telephone wire, made from such steel, is disadvantageous becausefit increases the electrical resistance and the hardness of the base wire. Our invention will eliminate the necessity for additions of phosphorusto the molten steel, whichis to be subsequently galvanized,

thephosphorus being introduced only into the surface layer of the solid steel, preferably in the drawn wire, although it may be introduced into the surface layer of the solid steel at any time after its solidification in the ingot mold; therefore, we are able to obtain the beneficial effects of the presence of phosphorus in the surface layer of the steel during galvanizing at-the same time avoiding the detrimental effect of phosphoruson the electrical and physical properties of the steel base such as electrical resistance, tensile strength and elongation.

As one example of the use of the invention we will describe the production of zinc coated telephone wire as follows:

The'cold drawn wire first having been drawn to the desired gauge is preferably passed through-the usual muriatic acid bath for cleaning, then is passed through a water bath to wash off the iron chloride and muriatic acid. The cleaned wire is then passed through an annealing chamber containing phosphine gas. From the annealing chamber the wire is passed, without contact with the air, directlyinto the molten zinc bath. The wire leaves the zinc bath preferably in a vertical direction through the usual charcoal cover and after cooling is coiled on takeup blocks. V

In our preferred practice the annealing chamber is sealed on the entering end with a fluid seal; the exit end of said chamber is sealed by havingthat end immersed in a molten zinc bath. I

We have found that we are-able to simultaneously anneal the wire and cause the dissociation of the phosphine into its elements. The hot wire being in contact with the phosphine, dissociates the phosphine, .the wire physically absorbing the phosphorus atoms in the surface layer. We have found that this action may be made to take place at different temperatures but we prefer to use a temperature ranging from 1250 to 1350 degrees F.. Through this temperature range we are able to both anneal and to phosphorizethe'surface layer of the wire. By passing the hot phosphorized wire directly into the molten zinc bath without contact with air, we .are able to obtain a greater bonding and alloying action between the iron or steel base and the zinc coating.

The depth of penetration of the phosphorus into the steel is dependent upon the rate at which the wire passes through the annealing chamber, the length of annealing v chamber and the temperature thereof. We

have found it sufficient and desirable to limit the time of phosphorizing to a relatively short period so as to obtain only a thin phosphorized surface layer.

By phosphorizing we mean the addition ofsmall quantities of the element phosphorus and no other element into the surface layer of the steel base. It is this element phosphorus alone which so affects the properties of the surface layer of the steel base as to cause the formation of a strongly adherent zinc coating when the steel base is subjected to galvanizing. Therefore, in the practice of our invention we add only phosphorus to the surface layer of the steel base and do not form a superficial iron phosphate coating as in the rust-proofing processes commonly known as Parkerizing, etc.

We are aware that phosphorizing, that is, the addition of phosphorus to the surface layer of a steel article, is not new and has been used to produce a rust-proof condition or coating on the surface of the steel article. In practicing our invention we do not use the addition of phosphorus to the surface layer of the steel base for rust-proofing, but use it to obtain a strong bond between the steel base and the zinc coating applied thereto. It should be pointed out that in the practice of addingphosphorus to the surface layer of the steel base for rust-proofing purposes the steel article is allowed to remain in contact with the phosphorizing'medium for a long period of time in order to produce a thick phosphorized surface layer. We difier from the last foregoing in that it is important that the steel wire be allowed to remain in contact with the phosphorizing medium for only a relatively short period of time, so as to produce onlya very thin phosphorized surface layer, in this way to so condition the surface layer of the steel wire so as to effect a strong bond between the steel base and the zinc coating. It is emphasized that the adding of phosphorus to the surface layer of a steel wire and the applying of the zinc coating to the so conditioned surface is a continuous process. We desire to be understood that we do not add the phosphorus to the surface layer of the wire for increasing the rust resisting qualities of the wire. The phosphorized surface layer we produce is so very thin that the rust resisting properties of the wire are not appreciably increased. The very thin phosphorized layer is only used as a means of increasing the adhesion or cohesion between the steel base and the zinc coating. 'The zinc-coated wire so produced, as heretofore pointed out, is capable of withstanding sever bending or "forming such as bending around its own diameter without flaking or peeling of the zinc coating.

As an alternative procedure we have found that very good results may be obtained by first passing the wire through an annealing chamber containing phosphine and then subsequently cooling the phosphorized wire,

While we have discussed the use of phosphine gas as a phosphorizing medium, it is to be understood that any compound of phosphorus, either gaseous, liquid or solid which at elevated temperatures. will dissociateto ,give free phosphorus atoms or molecules which in turn would be physically absorbed by the surface layer of the hot iron or steel base may be used as a phosphorizing medi- While we have described in connection with the invention the use of zinc as a protective coating on a phosphorized iron or steel article, we have in mind that other coatings may be used as, for example, lead, tin, cadmium, copper, nickel or aluminum, etc.

The terms and expressions which we have employed are used as terms of description and not of limitation and we have no intention in the use of such terms and expressions, of excluding any equivalent for the features shown and described, but recognize that various modifications are possible within the scope of the invention claimed.

\Vhat we claim is:

1. A zinc-coated iron or steel article, comprising a ferrous base, which has as an integral part of the base a phosphorized superficial layer containing'phosphorus in excess of that contained in the interior of the article base, and a coating of zinc alloyed to said phosphorized surface.

2. The process of zinc-coating an iron or steel article, which consists in subjecting the article base to an atmosphere of phosphine at a temperature and for a period of time sufiicient to produce a thin surface layer of high phosphorus content as an integral part of said base, and subsequently zinc coating said base by the hot-dip galvanizing process.

3. The process of zinc-coating an iron or steel article, which consists in subjecting the article'base to a phosphorizing medium at a temperature and for a period of time sufli-' cient to produce a thin surface layer of high phosphorus content as an integral part of said base, and subsequently zinc-coating said base by the hot-dip galvanizing process.

4. The process of zinc-coating an iron or steel article, which consists in subjecting the article base to a phosphorizing medium at a temperature and for a period of time sufficient to produce a thin surface layer of high phosphorous content as ,an integral part of said base, and subsequently zinccoating said base by passing it directly into molten zinc without contact with air.

5. The process of zinc-coating an iron or steel article, which consists in annealing said article and during such annealing to simultaneously produce a thin surface layer of high phosphorous content as an integral part of said base, and zinc-coating said article by passing it directly into molten zinc without the article cooling or coming into contact with air.

6. The process of continuously zinc-coatingwith air.

EDWARD J. P. FISHER. CLYDE C. CRANE. 

